Downhole valve assemblies can be used to selectively treat and/or produce wellbores. In treat and produce operations (“TAP”), for example, downhole valves are placed in a casing string and the wellbore is completed with normal cementing operations. The downhole valves are typically opened one at a time to selectively fracture hydrocarbon producing zones or formations within the wellbore. Consequently, TAP operations can be performed without a perforation treatment.
One way to actuate the downhole valves is to use a “ball” in combination with a restriction to provide a go/no-go triggering mechanism. When the outer diameter of the ball is smaller than the restriction in the valve, the ball can pass through the valve and the valve will remain in a closed position. When the outer diameter of the ball is larger than the restriction in the valve, the ball is stopped by the restriction in the valve actuating the valve. However, the use of a ball in combination with a restriction in the valve can be problematic because the number of downhole valves that can be used is limited by the diameter of the wellbore.
Another way to actuate the downhole valves is to use a control line. Generally, the control line can pressurize a piston in a sliding sleeve valve. The piston can squeeze a c-ring within the sliding sleeve valve and can reduce the inside diameter of the c-ring. When the c-ring has a reduced diameter, the c-ring can catch a downhole dart. Pressure can be applied to the dart causing the dart to longitudinally move the sliding sleeve. This method can be repeated for each valve disposed downhole. However, using a control line to actuate a downhole valve can be problematic because the control line can become damaged. A damaged control line can prevent actuation of the downhole valves.
There is a need, therefore, for a downhole valve triggering mechanism that is not limited by the diameter of the wellbore and that does not require a control line.